The present invention relates to a ceramic electronic device having a ceramic element and an external electrode on the ceramic element, and to a method of manufacturing the device.
A multi-layer ceramic capacitor will be explained as a known ceramic electronic device.
FIG. 4 is a cross sectional view of a conventional multi-layer ceramic capacitor. The multi-layer ceramic capacitor 21 includes a ceramic element 24 and external electrodes 29, 30 provided on both sides of the ceramic element 24. The ceramic element 24 is formed through sintering alternate layers of dielectric ceramic 22 and internal electrode 23. The external electrodes 29, 30 include respective external electrode bases 25, 26 connected to their corresponding internal electrodes 23, nickel-plating layers 27 joined to the external electrode bases 25, 26, and solder- or tin-plating layers 28, respectively.
A method of manufacturing the conventional multi-layer ceramic capacitor 21 will be explained.
First, the dielectric ceramics 22 and the internal electrode 23 are placed and bonded alternately one over the other, and sintered together at a high temperature, thus providing the ceramic element 24.
Then, the ceramic element 24 has both sides to which a pattern of electrode paste is applied, and is sintered, thus providing the external electrode bases 25, 26. The material of the paste is identical to that of the internal electrode 23 or its alloy. Then, the nickel-plating layer 27 for improving the operational reliability and the solder-friendly characteristics is provided on each of the external electrode bases 25, 26. The solder- or tin-plating layer 28 is provided on the nickel-plating layer 27, thus providing each of the external electrodes 29 and 30. Then, a multi-layer ceramic capacitor 21 is provided.
The ceramic element 24 in the conventional multi-layer ceramic capacitor 21 may however be susceptible in its surface insulating properties to the environmental conditions. In particular, the insulating properties between the external electrodes 29 and 30 may possibly be declined under humid conditions.
Also, when the ceramic element 24 is wet at its surface with water, the solder- or tin-plating 28 may develop migration of metal, thus short-circuiting between the external electrodes 29 and 30. The plating layer 28 may be oxidized with absorbing water, hence declining its soldering performance.
A ceramic electronic device and a method of manufacturing the device are provided. The device has an improved insulating and soldering properties thus having an increased operational reliability.
The ceramic electronic device includes a ceramic element, an external electrode provided on the ceramic element, and a protective layer provided on the ceramic element. The protective layer is formed through impregnating and dehydrating condensation of a composition expressed by Rxe2x80x94CnH2nxe2x80x94Sixe2x80x94(ORxe2x80x2)3 (where R is epoxy, alkyl, aryl, perfluoroaryl, or mixture of them, n is a natural number, and Rxe2x80x2 is an alkyl group having 1 to 4 carbon atoms, hydrogen, or halogen atom, wherein at least one of Rxe2x80x2 is hydrogen).